One prior water pump used for cooling an outboard engine utilized a cast metal housing. The cast metal housing requires machining and is costly to manufacture. Also, the life of a cast brass or cast aluminum water pump is relatively low where the water contains sand and silt which will cause internal wear on the moving parts.
Another prior water pump is formed of a molded plastic housing. A metal liner is used within the plastic housing to provide abrasion resistance. Without the metal liner the plastic will wear through resulting in a water pump failure. A water pump failure may also result in engine failure.